114 PLANT LIFE OK THE PARM. 



only generalities can here be alluded to. The cultivator 

 must observe for himself whether the plants he wishes to 

 grow are naturally shallow or deep-rooted ; whether the 

 roots break up into a dense leash of fine fibres encom- 

 passing and traversing in all directions the soil within a 

 certain limited area; or whether, as in the case of 

 lucerne, the "root" consists of a long, thick under- 

 ground stem, capable of extending itself for many feet, 

 and giving off, within a small extent, only a compara- 

 tively small number of fibres. The different forms of 

 roots previously alluded to may be looked on as adapta- 

 tions to different . conditions of the soil, especially in 

 relation to water, and the choice of site and mode of 

 tillage must be governed by circumstances. Leaf-de- 

 velopment is thus consequent on root-growth but, in 

 addition, an adequate supply of moisture and heat and 

 full exposure to light are demanded. The adjustment 

 of these agencies is rarely under the control of the far- 

 mer to anything like the same extent that it is in the 

 case of the gardener. The gradener can often contrive, 

 for instance, by appropriate modifications of treatment, 

 to keep his plants in a growing condition, and to prevent 

 them from " bolting " into flower, whereas the agricul- 

 turist is much more the slave of circumstances. Drouth 

 and heat check his crops before their growth is complete, 

 and induce premature development of fibre, of flower, or 

 of seed. Excessive moisture and superfluity of rich food 

 will cause the crops to become too rank in their growth, 

 to develop immature succulent tissue, comparatively 

 devoid of the nutritious secretions in which their value 

 consists, and will check the development of flowers. 



The observant eye of the farmer soon detects the un- 

 healthy state of the crops by the color of the leaves. If, 

 from any cause, root-action is deficient, or sun-heat and 

 sunlight are lacking, the chlorophyll is not formed in 

 sufficient amount, or is imperfectly developed, and the 



